Wherever you go today in DFW, take your umbrella

That 40 percent chance of rain was rapidly a sure thing for some parts of the Dallas-Fort Worth area early Tuesday as rain was already falling in Dallas and parts of Tarrant County.

An isolated shower was falling early Tuesday at the Rangers Ballpark in Arlington, said Steve Fano, meteorologist with the National Weather Service in Fort Worth.

The shower in Arlington was brief, but weather service forecasters were holding with the forecast calling for a 40 percent chance of afternoon thundershowers across the North Texas areas. The highs could reach the lower 80s, forecasters said.

A Pacific cold front at about 8 a.m. crossed the Red River and pushed south into North Texas where it's linking with an abundance of moist air from the Gulf of Mexico.

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"Showers are popping up ahead of the front from Arlington to northern Dallas County and on to Hunt County," Fano said. "Leading up to the first pitch, we'll have cloudy skies, and it will be warm and humid.

"The front is on schedule and it looks like thunderstorms could happen. I know that's not what anybody wants to hear, but maybe the storms will give the Rangers a little electrifying start this year."

POSSIBILITY FOR RAIN

The National Weather Service officials attache a percentage to their rain predictions for precipitation, but the system they use involves a "12-hour probability of precipitation or POP12." This refers to the likelihood, expressed as a percent, of a measurable precipitation event (1/100th of an inch or more) during the 12-hour period in a particular area.

In our case that generally means Tarrant and Dallas Counties -- the Metroplex.

The POP, usually for rain or snow, can be illustrated by an example, so let's use today, which calls for 40 percent probability of rain in the Metroplex. This means that there's a four-in-10 chance that any location in the Metroplex will receive at least 1/100th of an inch of rain.